Download To Beat or Not To Beat: Canine Heat Disease

To Beat or Not To Beat: Canine Heat Disease
By Stephen M. Sheldon, DVM
Heart disease is one of the most common medical problems in dogs. It is defined as any
destructive process within the heart. Your dog's heart is one of the most important organs:
it supplies the body's tissues and organs with oxygen and nutrients. Simply put, the right
side of the heart collects venous blood which is oxygen-poor and sends it to the lungs to
pick up much needed oxygen. Oxygen-rich blood then returns to the left side of the heart,
which then pumps it to the rest of the body.
Heart disease is caused by defects in the heart valves or muscle, trauma, tumors, and
heartworms. There are two types: congenital and acquired. Congenital defects are present
at birth and are rare. Some examples are patent Ductus Arteriousus (PDA) and pulmonic
stenosis. (These may sound familiar if you know pediatric medicine.) Acquired defects
usually develop during middle to old age. The most common types are chronic valvular
Disease (CVD) and Dilated Cardiomyopathy (DCM). CVD is more commonly referred to
as mitral regurgitation or valvular insufficiency; the tricuspid valve is less often affected.
The heart's valves act to ensure that blood flows properly through the heart in a forward
direction. If the valves "leak," blood can flow in a reverse direction. The result is a heart
murmur. To compensate for any inefficiency, the heart responds by pumping harder and
faster; symptoms of heart failure ensure. CVD can develop in any dog but certain breeds
are more susceptible. Poodles, Cocker Spaniels, Chihuahuas, and Llasa Apsos are some
examples. Larger breed dogs like Dobermans, Boxers, and Great Danes are more prone to
develop cardiomyopathy. Cardiomyopathy causes the muscular walls of the heart to
become thin and weak, and the chambers of the heart begin to dilate. Like CVD, an
inefficient heart is the result and signs of heart failure develop. We aren't really sure what
causes DCM; some researchers are looking at dietary carnitine or a virus as the cause.
Some forms are also hereditary.
The early signs of heart failure often go unnoticed; sometimes only a drop off in activity
is noticed. Early signs of heart failure are exercise intolerance and a cough when
exercising or when excited. These symptoms become more severe as the disease
progresses; additionally, other signs develop such as rapid breathing, abdominal swelling,
and weight loss. These symptoms appear because the heart can not accurately pump
enough blood to meet the body's needs. This may cause blood to back up in the lungs,
kidneys, and/or liver. What results is fluid leaking into these organs causing congestion
and organ failure.
If you are seeing these symptoms, see your veterinarian. He or she will perform a
thorough exam which should include ausculting the heart and lungs with a stethoscope,
taking the pulse, examining gums and mucous membranes and palpating the abdomen to
check for fluid accumulations or enlarged organs.
Diagnostic procedures will probably be recommended. Chest Radiographs help show the
size and shape of the heart as well as the condition of the lungs. Electrocardiograms
(ECG) show heart rate, regularity and chamber size. Complete Blood Cell Counts CBC),
Blood Chemistries (SMAC) and urinalysis (UA) help assess the immune system, liver,
kidney, and other organs. Echocardiograms (ultrasound) help visualize the chambers and
valves of the heart. Echoes are extremely helpful in diagnosing and monitoring heart
conditions, but unfortunately many general practitioners do not have the capability to
perform them in their offices.
Therapy of heart disease entails "managing" the symptoms. We say "manage" rather than
"cure" or "treat" because most of the underlying causes are permanent and progressive.
Depending on which authors you read, heart failure patients are categorized in either 3 or
4 categories; it is purely academic as patient's flow regularly from one category to
another. Category 1 patients are usually without symptoms and are managed by
restricting exercise and placing them on sodium restricted diet. (Sound familiar?) When
symptoms present, patients are managed with one or all of the following classes of drugs:
Preload drugs reduce the blood volume presented to the heart; they are diuretics and/or
venous dilators. Less volume presented to the heart means less work. Afterload drugs
help reduce blood pressure, they are arterial dilators. A simple way to see how blood
pressure makes the heart work harder is to try and blow up a balloon with your hands
squeezing the balloon, now take your hand off and see how easier it gets. These drugs are
relatively new for animals and we're seeing great results. The third class of drugs helps
Contractility. They help the heart muscle contract more forcefully.
It all sounds pretty straightforward, right? Actually, managing these patients is more art
than science. Experience and the ability to monitor response to treatment are essential in
succeeding. Early diagnosis can also slow the progressive nature of these diseases; if you
see signs, seek professional advice as soon as possible.